This post is a collection of information on the supposed genetic relation of Native Americans to Western Eurasians.
The 24,000-year-old remains of a young boy from the Siberian village of Mal’ta have added a new root to the family tree of indigenous Americans. While some of the New World’s native ancestry clearly traces back to east Asia, the Mal’ta boy’s genome — the oldest known of any modern human — shows that up to one-third of that ancestry can be traced back to Europe.
The results show that people related to western Eurasians had spread further east than anyone had suspected, and lived in Siberia during the coldest parts of the last Ice Age.
“At some point in the past, a branch of east Asians and a branch of western Eurasians met each other and had sex a lot,” says palaeogeneticist Eske Willerslev at the University of Copenhagen, who led the sequencing of the boy’s genome. This mixing, he says, created Native Americans — in the sense of the populations of both North and South America that predated — as we know them. His team’s results are published in Nature.
In 2009, Willerslev’s team travelled to Hermitage State Museum in St. Petersburg, where it had arranged to collect a DNA sample from one of the Mal’ta boy’s arm bones. “We hoped that he could tell us something about the early peopling of the Americas, but it was a complete long shot,” he says.
The team found that DNA from the boy’s mitochondria — the energy-processing organelles of living cells — belonged to a lineage called haplogroup U, which is found in Europe and west Asia but not in east Asia, where his body was unearthed. The result was so bizarre that Willerslev assumed that his sample had been contaminated with other genetic material, and put the project on hold for a year.
But the boy’s nuclear DNA — the bulk of his genome — told the same story. “Genetically, this individual had no east Asian resemblance but looked like Europeans and people from west Asia,” says Willerslev. “But the thing that was really mind-blowing was that there were signatures you only see in today’s Native Americans.” This signal is consistent among peoples from across the Americas, implying that it could not have come from European settlers who arrived after Christopher Columbus. Instead, it must reflect an ancient ancestry.
The Mal’ta boy’s genome showed that Native Americans can trace 14% to 38% of their ancestry back to western Eurasia, the authors conclude.
“The distribution of genetic lineages 24,000 years ago must have been quite different from what we see today,” says Jennifer Raff, an anthropologist and geneticist from the University of Texas at Austin. “It would be very interesting to see what other genomes from this time period look like.”
Willerslev’s team suggests that after the ancestors of Native Americans split off from those of east Asians, they moved north. Somewhere in Siberia, they met another group of people coming east from western Eurasia — the people to whom the Mal’ta boy belonged. The two groups mingled, and their descendants eventually travelled east into North America.
“We already had strong evidence of Siberian ancestry for Native Americans; this study is important because it helps us understand who the ancestors of those Siberians might have been,” says Raff.
This new origin story helps to resolve several peculiarities in New World archaeology. For example, ancient skulls found in both North and South America have features that do not resemble those of East Asians. They also carry the mitochondrial haplogroup X, which is related to western Eurasian lineages but not to east Asian ones.
On the basis of these features, some scientists have suggested that Native Americans descended from Europeans who sailed west across the Atlantic. However, says Willerslev, “you don’t need a hypothesis that extreme”. These features make sense when you consider that Native Americans have some western Eurasian roots.
“There remains some debate about whether there was a single expansion of human groups into the Americas or more than one,” says Theodore Schurr, an anthropologist from the University of Pennsylvania in Philadelphia. “The data from this paper support a single-migration scenario,” he says, but still allows for several sequential ones from the same intermingled Siberian gene pool.
Abstract The origins of the First Americans remain contentious. Although Native Americans seem to be genetically most closely related to east Asians there is no consensus with regard to which specific Old World populations they are closest to. Here we sequence the draft genome of an approximately 24,000-year-old individual (MA-1), from Mal’ta in south-central Siberia, to an average depth of 1×. To our knowledge this is the oldest anatomically modern human genome reported to date. The MA-1 mitochondrial genome belongs to haplogroup U, which has also been found at high frequency among Upper Palaeolithic and Mesolithic European hunter-gatherers, and the Y chromosome of MA-1 is basal to modern-day western Eurasians and near the root of most Native American lineages. Similarly, we find autosomal evidence that MA-1 is basal to modern-day western Eurasians and genetically closely related to modern-day Native Americans, with no close affinity to east Asians. This suggests that populations related to contemporary western Eurasians had a more north-easterly distribution 24,000 years ago than commonly thought. Furthermore, we estimate that 14 to 38% of Native American ancestry may originate through gene flow from this ancient population. This is likely to have occurred after the divergence of Native American ancestors from east Asian ancestors, but before the diversification of Native American populations in the New World. Gene flow from the MA-1 lineage into Native American ancestors could explain why several crania from the First Americans have been reported as bearing morphological characteristics that do not resemble those of east Asians. Sequencing of another south-central Siberian, Afontova Gora-2 dating to approximately 17,000 years ago, revealed similar autosomal genetic signatures as MA-1, suggesting that the region was continuously occupied by humans throughout the Last Glacial Maximum. Our findings reveal that western Eurasian genetic signatures in modern-day Native Americans derive not only from post-Columbian admixture, as commonly thought, but also from a mixed ancestry of the First Americans.
(Source: “Upper Palaeolithic Siberian genome reveals dual ancestry of Native Americans”, by Maanasa Raghavan et al.)
Genetic analysis of ancient DNA from a 6-week-old infant found at an Interior Alaska archaeological site has revealed a previously unknown population of ancient people in North America.
The findings, published in the Jan. 3 edition of the journal Nature, represent a major shift in scientists’ theories about how humans populated North America. The researchers have named the new group “Ancient Beringians.”
“We didn’t know this population existed,” said Ben Potter, one of the lead authors of the study and a professor of anthropology at the University of Alaska Fairbanks. “These data also provide the first direct evidence of the initial founding Native American population, which sheds new light on how these early populations were migrating and settling throughout North America.”
Genetic analysis and demographic modeling, which help scientists draw connections among groups of people over time, indicate that a single founding ancestral Native American group split from East Asians about 35,000 year ago. Then, about 20,000 years ago, that group split into two groups: the Ancient Beringians and the ancestors of all other Native Americans. Lead authors J. Victor Moreno-Mayar, Eske Willerslev and the team at the Centre for GeoGenetics at the University of Copenhagen’s Natural History Museum of Denmark completed the genetics work.
The DNA from the infant, named “Xach’itee’aanenh T’eede Gaay” (sunrise girl-child) by the local indigenous community, has provided an unprecedented window into the history of her people, Potter said. She and a younger female infant found at the Upward Sun River site in 2013 lived about 11,500 years ago and were closely related, likely first cousins. The younger infant has been named “Ye?kaanenh T’eede Gaay” (dawn twilight girl-child).
“It would be difficult to overstate the importance of this newly revealed people to our understanding of how ancient populations came to inhabit the Americas,” Potter said. “This new information will allow us a more accurate picture of Native American prehistory. It is markedly more complex than we thought.”
The findings also suggest two new scenarios for populating the New World. One is that there were two distinct groups of people who crossed over the Beringian land bridge prior to 15,700 years ago. A second is that one group of people crossed over the land bridge and then split in Beringia into two groups: Ancient Beringians and other Native Americans, with the latter moving south of the ice sheets 15,700 years ago.
Potter’s National Science Foundation-funded work at the Upward Sun River site has spanned a decade. He said that when the science team began the analysis of the genetic material, they expected it to match the genetic profile of other northern Native American people. Instead, it matched no other known ancient population.
What this suggests is that the Ancient Beringian people remained in the Far North for thousands of years, while the ancestors of other Native American peoples spread south throughout the rest of North America. The DNA results, along with other archaeological data, suggest that Athabascan ancestors moved north again, possibly around 6,000 years ago, eventually absorbing or replacing the Ancient Beringian population and establishing deep roots in their ancestral lands.
“There is very limited genetic information about modern Alaska Athabascan people,” Potter said. “These findings create opportunities for Alaska Native people to gain new knowledge about their own connections to both the northern Native American and Ancient Beringian people.”
Nearly one-third of Native American genes come from west Eurasian people linked to the Middle East and Europe, rather than entirely from East Asians as previously thought, according to a newly sequenced genome.
Based on the arm bone of a 24,000-year-old Siberian youth, the research could uncover new origins for America’s indigenous peoples, as well as stir up fresh debate on Native American identities, experts say.
The study authors believe the new study could also help resolve some long-standing puzzles on the peopling of the New World, which include genetic oddities and archaeological inconsistencies.
“These results were a great surprise to us,” said study co-author and ancient-DNA specialist Eske Willerslev, of the University of Copenhagen, Denmark.
“I hadn’t expected anything like this. A genome related to present-day western Eurasian populations and modern Native Americans as well was really puzzling in the beginning. How could this happen?”
So what’s new?
The arm bone of a three-year-old boy from the Mal’ta site near the shores of Lake Baikal in south-central Siberia (map) yielded what may be the oldest genome of modern humans ever sequenced.
DNA from the remains revealed genes found today in western Eurasians in the Middle East and Europe, as well as other aspects unique to Native Americans, but no evidence of any relation to modern East Asians.
A second individual genome sequenced from material found at the site and dated to 17,000 years ago revealed a similar genetic structure.
It also provided evidence that humans occupied this region of Siberia throughout the entire brutally cold period of the Last Glacial Maximum, which ended about 13,000 years ago.
Why is it important?
Prevailing theories suggest that Native Americans are descended from a group of East Asians who crossed the Bering Sea via a land bridge perhaps 16,500 years ago, though some sites may evidence an earlier arrival.
“This study changes this idea because it shows that a significant minority of Native American ancestry actually derives not from East Asia but from a people related to present-day western Eurasians,” Willerslev said.
“It’s approximately one-third of the genome, and that is a lot,” he added. “So in that regard I think it’s changing quite a bit of the history.”
While the land bridge still formed the gateway to America, the study now portrays Native Americans as a group derived from the meeting of two different populations, one ancestral to East Asians and the other related to western Eurasians, explained Willerslev, whose research was published in the November 20 edition of the journal Nature.
“The meeting of those two groups is what formed Native Americans as we know them.”
What does this mean?
Willerslev believes the discovery provides simpler and more likely explanations to long-standing controversies related to the peopling of the Americas.
“Although we know that North Americans are related to East Asians, it’s striking that no contemporary East Asian populations really resemble Native Americans,” he said.
“It’s not like you can say that they are really closely related to Japanese, Chinese, or Koreans, so there seems to be something missing. But this result makes a lot of sense regarding why they don’t fit so well genetically with contemporary East Asians—because one-third of their genome is derived from another population.”
The findings could also allow reinterpretation of archaeological and anthropological evidence, like the famed Kennewick Man, whose remains don’t look much like modern-day Native American or East Asian populations, according to some interpretations.
“Maybe, if he looks like something else, it’s because a third of his ancestry isn’t coming from East Asia but from something like the western Eurasians.”
Many questions remain unanswered, including where and when the mixing of west Eurasian and East Asian populations occurred.
“It could have been somewhere in Siberia or potentially in the New World,” Willerslev said.
“I think it’s much more likely that it occurred in the Old World. But the only way to address that question would be to sequence more ancient skeletons of Native Americans and also Siberians.”
Intriguing questions also exist about the nature of the advanced Upper Paleolithic Mal’ta society that now appears to figure in Native American genomes.
The Siberian child “was found buried with all kinds of cultural items, including Venus figurines, which have been found from Lake Baikal west all the way to Europe.
“So now we know that the individual represented with this culture is a western Eurasian, even though he was found very far east. It’s an interesting question how closely related this individual might have been to the individuals carving these figurines at the same time in Europe and elsewhere.”
Research-Selection for NovoScriptorium: Maximus E. Niles